ASTM E424-71(2007)

Standard Test Methods for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials

SIGNIFICANCE AND USE
Solar-energy transmittance and reflectance are important factors in the heat admission through fenestration, most commonly through glass or plastics. (See Appendix X3.) These methods provide a means of measuring these factors under fixed conditions of incidence and viewing. While the data may be of assistance to designers in the selection and specification of glazing materials, the solar-energy transmittance and reflectance are not sufficient to define the rate of heat transfer without information on other important factors. The methods have been found practical for both transparent and translucent materials as well as for those with transmittances reduced by highly reflective coatings. Method B is particularly suitable for the measurement of transmittance of inhomogeneous, patterned, or corrugated materials since the transmittance is averaged over a large area.
SCOPE
1.1 These test methods cover the measurement of solar energy transmittance and reflectance (terrestrial) of materials in sheet form. Method A, using a spectrophotometer, is applicable for both transmittance and reflectance and is the referee method. Method B is applicable only for measurement of transmittance using a pyranometer in an enclosure and the sun as the energy source. Specimens for Method A are limited in size by the geometry of the spectrophotometer while Method B requires a specimen 0.61 m2 (2 ft2). For the materials studied by the drafting task group, both test methods give essentially equivalent results.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 28-Feb-2007
• ICS: 83.140.10 - Films and sheets
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources

Relations

• Replaces: ASTM E424-71(2001) - Standard Test Methods for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials
• Effective Date: 01-Mar-2007
• Referred By: ASTM D4851-07(2019)e1 - Standard Test Methods for Coated and Laminated Fabrics for Architectural Use
• Effective Date: 01-Mar-2007
• Referred By: ASTM E903-20 - Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres
• Effective Date: 01-Mar-2007
• Referred By: ASTM G214-23 - Standard Test Method for Integration of Digital Spectral Data for Weathering and Durability Applications
• Effective Date: 01-Mar-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E424 −71(Reapproved 2007)
Standard Test Methods for
Solar Energy Transmittance and Reflectance (Terrestrial) of
1
Sheet Materials
This standard is issued under the fixed designation E424; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3. Definitions
1.1 These test methods cover the measurement of solar
3.1 solar absorptance—the ratio of absorbed to incident
energytransmittanceandreflectance(terrestrial)ofmaterialsin
radiant solar energy (equal to unity minus the reflectance and
sheetform.MethodA,usingaspectrophotometer,isapplicable
transmittance).
for both transmittance and reflectance and is the referee
3.2 solar admittance—solar heat transfer taking into ac-
method. Method B is applicable only for measurement of
count reradiated and convected energy.
transmittance using a pyranometer in an enclosure and the sun
as the energy source. Specimens for Method A are limited in
3.3 solar energy—for these methods the direct radiation
sizebythegeometryofthespectrophotometerwhileMethodB from the sun at sea level over the solar spectrum as defined in
2 2
requires a specimen 0.61 m (2 ft ). For the materials studied
3.2, its intensity being expressed in watts per unit area.
by the drafting task group, both test methods give essentially
3.4 solar reflectance—the percent of solar radiation (watts/
equivalent results.
unit area) reflected by a material.
1.2 This standard does not purport to address all of the
3.5 solar spectrum—for the purposes of these methods the
safety problems, if any, associated with its use. It is the
solar spectrum at sea level extending from 350 to 2500 nm.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.6 solar transmittance—the percent of solar radiation
bility of regulatory limitations prior to use.
(watts/unit area) transmitted by a material.
2. Referenced Documents
4. Summary of Methods
2
2.1 ASTM Standards:
4.1 Method A—Measurements of spectral transmittance, or
E259Practice for Preparation of Pressed Powder White
reflectance versusamagnesiumoxidestandard,aremadeusing
Reflectance Factor Transfer Standards for Hemispherical
anintegratingspherespectrophotometeroverthespectralrange
and Bi-Directional Geometries
from350to2500nm.Theilluminationandviewingmodeshall
E275PracticeforDescribingandMeasuringPerformanceof
be normal-diffuse or diffuse-normal. The solar energy trans-
Ultraviolet and Visible Spectrophotometers
mitted or reflected is obtained by integrating over a standard
E308PracticeforComputingtheColorsofObjectsbyUsing
solar energy distribution curve using weighted or selected
the CIE System
ordinates for the appropriate solar-energy distribution. The
distribution at sea level, air mass 2, is used.
1
These test methods are under the jurisdiction of ASTM Committee E44 on
Solar, Geothermal and Other Alternative Energy Sources and is the direct respon- 4.2 Method B—Using the sun as the source and a pyranom-
sibility of Subcommittee E44.05 on Solar Heating and Cooling Systems and
eter as a detector the specimen is made the cover of an
Materials.
enclosure with the plane of the specimen perpendicular to the
Current edition approved March 1, 2007. Published April 2007. Originally
incidentradiation;transmittanceismeasuredastheratioofthe
approved in 1971. Last previous edition approved in 2001 as E424-71(2001). DOI:
10.1520/E0424-71R07.
energy transmitted to the incident energy. (The apparatus of
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Method B has been used for the measurement of solar-energy
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
reflectance but there is insufficient experience with this tech-
Standards volume information, refer to the standard’s Document Summary page on
nique for standardization at present.)
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E424−71 (2007)
5. Significance and Use is recommended that the specimen be placed in direct contact
with the sphere to minimize and control loss of scattered
5.1 Solar-energytransmittanceandreflectanceareimportant
radiation.
factors in the heat admission through fenestration, most com-
6.2.3 For specularly reflecting specimens the sphere
monly through glass or plastics. (See Appendix X3.) These
conditions, especially where the reflected beam strikes the
method
...